Ventilated smoking article

ABSTRACT

The invention concerns a smoking article filter plug ( 16 ) for a cigarette, the filter plug being cylindrical and having a plug wrap ( 18 ), grooves ( 20 ) being impressed into the plug wrap, and a tipping paper ( 22 ) for the attachment of the filter plug to the tobacco rod ( 12 ). Some grooves are axially extending with respect to the axis of the filter plug and are open on the side of the tobacco rod and extend continuously only over a part of the length of the filter plug. All grooves are covered by a ventilated tipping paper, which allows ventilating air into the axially extending grooves only. In addition, the invention concerns the use of such a filter for the reduction of the CO/tar ratio as a function of the filter ventilation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This current application is a divisional patent application that claimspriority to and benefit from, currently pending, U.S. patent applicationSer. No. 10/499,281, filed on Jun. 18, 2004, which is a 35 U.S.C. §371PCT 30 Month National Stage filing of PCT/GB02/05603, filed on Dec. 11,2002, which claims priority to and benefit from European PatentApplication Serial Number EP 01129382.6, filed on Dec. 18, 2001.

DESCRIPTION OF THE INVENTION

The invention relates to a smoking article, in particular but notexclusively a cigarette, incorporating a filter in which grooves arepressed into the circumference of the filter.

Various forms of embodiment of such filters are known. Thus U.S. Pat.No. 4,406,294 discloses a cigarette filter with a cylindrical filterplug, with an air-permeable plug wrap for the filter plug and withgrooves impressed into the circumference of the filter plug extendingover a part of the filter length from the mouth end of the filter. Thegrooves are, however, impermeable. The cylindrical filter plug and hencealso the grooves are attached by an air-permeable tipping paper providedwith ventilation openings. The filter has an uncomplicated structure andachieves an essentially normal drop in pressure over the cigarette.

U.S. Pat. No. 4,256,122 discloses a cigarette filter with a similarstructure, where, however, the circumferential surface of the filterplug, including the walls of the grooves, are impermeable by virtue ofan impermeable plug wrap. Here, though, some of the grooves are open atthe mouth end of the filter plug. FIGS. 2, 3 and 5 show embodimentswhich also include grooves which are still open on the tobacco end. Withthis filter a strong tobacco-flavoured cigarette is obtained whichretains, the high reduction of the unwanted smoke constituents and thegood processability on standard cigarette machines. However, some ofthese embodiments require precise registration of the perforated tippingwrapper with circumferential grooves, giving manufacturing and qualityproblems.

U.S. Pat. No. 4,649,943 shows a further modification of such a filter,in which the grooves are open at the mouth end of the filter. Inaddition, at least one perforation is provided in the area of thegrooves intended for the introduction of air through the plug wrap intothe filter plug, thereby providing the filter with an improved airdistribution in the filter rod. In addition a tipping wrapper ofimpermeable material which has an air-permeable region contributes tothis. The lining paper (plug wrap) is impermeable but provided withventilation openings.

Further, DE-PS 21 07 850 discloses a filter tip, the circumference ofwhich is provided with longitudinal grooves. A plug wrap is notmentioned and the grooves are preferentially open at the mouth end ofthe filter.

U.S. Pat. No. 4,362,171 discloses a cigarette filter with grooves whichare open neither at the tobacco end nor at the mouth end and thus extendonly over the centre of the filter plug. Each groove is provided with anopening, so that ventilation air is guided longitudinally along thefilter rod in the direction of the mouth end. Thus outside air isintroduced at high velocity in a simple manner into the cigarettefilter, without the danger of a blockage due to lip pressure and/or aloss of pressure.

U.S. Pat. No. 4,343,319 discloses a similar cigarette filter with asmoke-impermeable wrapper for the filter plug and with a central tube,extending axially through the filter plug, which is located in flowconnection with the opening in the grooves. In this way the smokeleaving the tobacco rod is divided into two parts. One part flowsthrough the central pipe and the other part flows through the filtermaterial. The presence of tubes and interconnecting passages adds to thecomplexity of the filter manufacture.

Further, a cigarette filter with an air-impermeable wrapper for thefilter core and with grooves in the circumference of the filter core andwhich extend over the whole length of the filter core is disclosed in DE30 48 905 A1. This filter can be manufactured more easily, since it isnot necessary to change the production direction.

A filter for tobacco smoke provided with grooves in its circumferencewhich are produced by a corrugated material around the actual filter isknown from GB 2102271. The plug wrap surrounding the filtration materialis smoke-impermeable. Grooves are provided between the plug wrap and thecorrugated material, and also between the tipping wrapper and thecorrugated material. The tipping wrapper is provided with ventilationopenings. This filter element should be versatile and flexibly usable.

GB 2 089 641 A discloses a filter for a cigarette with a central, hollowtube, which extends from one end of the filter into the filter material.The filter core is surrounded by a non-porous wrapper and the filterplug and the wrapper have at least one groove, which extendslongitudinally from one end of the filter plug. In this way a normaldecrease of pressure through the cigarette is achieved for a filter withlow to moderate efficiency. Formation of a hollow tube adds to themanufacturing requirements.

Further, GB 2 136669 A shows a cigarette filter with a filter plug whichis surrounded by a smoke-permeable material. The filter has longitudinalcorrugations which form grooves outside of the smoke-permeable wrapperwhich are open at one end of the filter and extend in longitudinaldirection from this end towards the other end but not over the entirelength of the filter plug. The smoke permeable wrapper carries means,i.e. a coating, which makes it smoke-impermeable over a region whichextends over only a part of the length of the grooves and separates fromthe corresponding end of the filter a grooved region of the wrapperwhich is smoke permeable.

GB 2 095 093 A discloses a filter with a filter plug with a non-porouswrapper and with grooves which extend from one end of the filter acertain distance in the direction of the other end of the filter. Thegrooves can be open to the atmosphere and so aligned that they extend upto the mouth end of the filter or to the tobacco end of the filter. Itis also possible to have an alternating arrangement of grooves whichbegin at the mouth end and at the tobacco end. The filter is fastened tothe tobacco rod by a narrow strip of material in order to preventdisruption of the entry of the ventilation openings to the grooves.

U.S. Pat. No. 3,752,165 shows a filter for a smokable article with afilter plug which is wrapped in a thin, porous wrapper paper. Aplurality of grooves is formed in the wrapper paper and into the filtermaterial at one end of the filter. The grooves extend from one end ofthe filter to a point shortly before the opposite end and are surroundedby a smoke-impermeable plug wrap. The grooves extend from one end of thefilter to a point which is some distance from the other end. A highefficiency for the removal of the tar from the tobacco smoke with anacceptable decrease of pressure can be achieved with this filter.

Further, a filter is known from U.S. Pat. No. 3,910,288 with a filterplug provided around its circumference with grooves which extend fromthe tobacco end of the filter up to a place before the mouth end of thefilter. The grooves are formed in a rigid plastic wrapper whichsurrounds the filter material. At one end of every groove an opening isprovided which makes a connection to the filter material possible.Filter ventilation is not provided.

This filter is very resistant to crushing, so that the and/or eachgroove can remain open during the entire smoking of the smokablearticle. By gradually changing the portion of the smoke which flowsthrough the groove from a previously defined value to a value of 0, thefilter achieves an almost homogeneous delivery of particulate materialper puff with a relatively constant increase of the degree of efficiencyof the filter.

Finally, U.S. Pat. No. 3,596,663 shows a filter for a smokable articlewith a filter plug with grooves, the length of which is not defined. Thefilter wrapper and the lining paper are in each case porous and/orprovided with perforations. The air-permeable wrapper is corrugated inorder to increase the size of the air-permeable surface and thus tosimplify the path of the air which is allowed through the ventilatedwrapping paper to the filter material of the filter plug. Thus aventilated filter is produced that significantly reduces the restrictionof the air passage to the filtering medium.

It can thus be stated in summary that for many years cigarette filtershave been provided with grooves which permit smoke and/or air to bedirected differently as a function of the position and the length of thegrooves and the porosity and/or ventilation of the tipping orfilter-wrapping paper. In this way it is possible to achieve a dilutionof the smoke, turbulence of the smoke in the mouth area, and theseparate guidance of ventilation air arid smoke, as well as some othereffects.

In recent years attention has been directed to one smoke component, i.e.carbon monoxide (CO), for which no effective, economical filter is yetknown. Particularly in view of the new legal requirements whichprescribe a maximum CO quantity in the tobacco smoke of a cigarette,attempts are being made to reduce the CO content of the smoke to below agiven maximum value.

The object of the invention is to produce a filter for a smokingarticle, in particular a cigarette, which enables an effective, inparticular adjustable, decrease of the CO content of the smoke comparedwith other components, such as tar and nicotine.

This is achieved in accordance with the invention by the features ofclaim 1.

Appropriate embodiments are defined by the characteristics of thesubordinate claims.

Due to the flow mechanics in the filter of this invention, the retentionof the filter material is reduced because of the well known dependencyof the linear flow velocity retention decreases with increasing flowvelocity. Due to the fact that the CO level is not affected by thefiltering material, the CO/tar ratio decreases.

If an air-impermeable plug wrap is used with the filter in accordancewith invention then the ventilating air flows over the grooves towardthe tobacco rod when smoking the cigarette and from there back throughthe filtration material into the mouth of the smoker.

As an alternative it is possible to employ a plug wrap which isinherently porous or ventilated and hence provided with ventilationopenings. Some of the ventilation air then flows through this path andhence through the permeable plug wrap into the filter and to the mouthof the smoker. This portion can be adjusted by appropriate adjustment ofthe inherent or artificial porosity of the plug wrap, by which means thepressure drop/smoking mechanics as well as the CO/tar ratio can also beinfluenced.

As a further alternative, porous or ventilated plastic sheets or foilsmay be used as plug wrap material.

The use of on-machine laser perforation of tipping paper and impermeableplugwrap is particularly useful for low delivery products with a tardelivery of less than 3 mg, preferably less than 1 mg. For such lowdelivery products it may be advantageous to provide two rows ofventilation holes, one row located above the axially extending groovesand another row located downstream of those holes. On-line machineperforation perforates both the plug wrap and the filtration materialunderneath, allowing the ingress of ventilating air thereto. Thus, mixedventilation occurs, i.e. through grooves and filtration material.

Synthetic or thermoformable plugwraps such as those described in BritishPatent Nos. 2058543, 2056841 or 2134365 may also be especially suitableas heat mouldable plug wrap for the present invention.

Experiments have shown that the CO/tar ratio attainable changes as afunction of the filter ventilation, i.e. the CO/tar ratio is reduced byincreasing the filter ventilation, providing a further correctingvariable for the CO/tar ratio.

In a preferred embodiment two to ten grooves are provided, since the useof only one groove leads to a very asymmetrical distribution of theventilation air in the smoke which could impair smoking enjoyment. Morethan ten grooves greatly complicate the production process and alsohardly leave enough space for adequate flow cross-section of theindividual grooves. Good results were achieved with four grooves.

The grooves have a V-shaped or preferably a U-shaped cross section,since this has manufacturing and rheological advantages.

By choosing the appropriate number of grooves, their appropriate depth,width and length it is possible to adjust the filter properties to thetarget properties of the cigarette to be produced.

All conventionally used filter materials may be employed as filtermaterial where one or several of these materials can be used. Preferablya conventional filter tow of cellulose acetate is used. For hardeningthe filters, conventional techniques are used, for example addingtriacetin or Tegda to the filter tow.

It is also possible to add additives, such as activated charcoal,zeolites, flavour modifiers or an ion exchange resin, such as that knownas Duolite (see U.S. Pat. No. 3,716,500 or 3,943,832) which is a porousparticulate salt of a weakly basic anion exchange resin, to the filterin order to reduce other vapour phase constituents.

Preferably the filtration material is homogeneous. As used hereinhomogeneous as applied to filtration material means there are no flowopenings, tubes or other elements in the filtration material. Ahomogeneous filtration material may, though, be comprised of differentfiltration materials, such as in differing filtration sections, shouldthe filter be a multiple filter. A homogeneous filtration material hasbenefits of simplicity in manufacture.

Preferably the additive is located in a region of the filter which doesnot have grooves. This prevents thermal decomposition of the additiveupon moulding to produce the grooves.

In accordance with a preferred embodiment the grooves extend over lessthan 80% of the length of the filter, where good results were obtainedwith about 60%.

The depth of the grooves should be within the range 0.5 to 2 mm,preferably about 1 mm, where suitable flow volumes are achieved.

Taking this criterion into consideration the width of the grooves,measured at the circumference of the filter, should lie between 1 and 3mm, preferentially between 1.5 and 2.5 mm.

The depth of the grooves along the rod axis may not necessarily beconstant it may for example increase towards the open end, the tobaccoside of the filter. The grooves may also be non-linear, following forexample a screwed or helical form around the filter.

In some cases it may be necessary that a further groove is added to thefilter, which runs radially around the filter circumference. This grooveshall connect the axial grooves. It is useful that this radial groove islocated directly below the ventilation zone of the tipping paper, whichenhances the ventilation effect. In cases of larger ventilation zones itmay also be necessary to use two or more radial grooves.

The filter of this invention may obviously be included as part of a dualor triple filtering device.

The tipping paper serving to attach the filter to the tobacco rod mayhave a conventional structure, provided that it permits ventilation.This can be achieved either by use of a porous, therefore inherentlyair-permeable tipping paper or by producing ventilation openings bymechanical or electrostatic means or using laser beams.

In order that the invention may be clearly understood and readilycarried into effect, reference will now be made, by way of example, tothe following diagrammatic drawings, in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a filter attached to a tobacco rodwith partly wrapped tipping paper,

FIG. 2 shows a curve plotting of the CO/tar ratio as a function of thefilter ventilation for a filter in accordance with the invention and acomparison filter,

FIG. 3 shows an embodiment of a filter with particulate additivetherein, and

FIG. 4 shows another embodiment of a filter with particulate additivetherein.

BRIEF DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a perspective view of a part of a proposed filter cigarettegenerally indicated by the reference symbol 10 with a conventionaltobacco rod 12 and a filter element 14 appended to one end of thetobacco rod 12. The filter element 14 consists of a cylindrical filterplug 16 of cellulose acetate tow as filtration material, which ishomogeneously distributed over the entire volume of the filter plug 14.Thus, no flow openings, tubes or other means are provided in the filterplug 16. As used herein ‘homogeneous’ as applied to filtration materialmeans there are no flow openings, tubes or other elements in thefiltration material. A homogeneous filtration material may, though, becomprised of different filtration materials, such as the differingfiltration sections described below with respect to FIG. 4, none ofwhich incorporate flow openings, tubes, etc.

The filter plug 16 is covered with a plug wrap 18 which isair-impermeable, although in other embodiments (not shown) it can beinherently porous and/or provided with ventilation openings dependingupon requirements, taking account particularly of the tobacco tastedesired.

Grooves 20 are stamped into the circumference of the filter element 14,four grooves 20 in the embodiment shown, which are distributedsymmetrically over the circumference of the filter element 14. Thegrooves 20 extend up to the tobacco rod end of the filter element 14,where they are open so that there is a flow connection between thegrooves 20 and the tobacco rod 12.

The grooves 20 run over the circumference of the filter plug 16 in anaxial direction and end at a rheologically adequate distance from themouth end of the filter element 14 and hence at a distance at whichneither air nor smoke from the grooves 20 can directly reach the mouthend of the filter element 14.

Investigations have shown that the axial length of the grooves 20 shouldbe less than 80% of the length of the filter plug 14. About 60% ispreferred.

The grooves 20 have a depth of approximately 1.5 mm and a U-shaped crosssection and a width of approximately 2 mm at the circumference.

The filter element 14 is surrounded in the usual way by a tipping paper22, which is provided in the embodiment shown with two circumferentialparallel rows of ventilation holes 24. A larger or smaller number ofrows of ventilation holes can also be provided or the tipping paper 22can be inherently porous. It is only necessary to ensure that theporosity and/or the number and size of the ventilation openings 22ensure the desired degree of ventilation.

For the arrangement of the plug wrap 18 there are in principle twopossibilities, i.e. the use of an air-impermeable paper or anair-permeable paper. In the case of use of an air-impermeable paper asplug wrap 18, ventilation air flows through the ventilation openings 24when smoking the cigarette into the grooves 20 and then from the grooves20 toward tobacco rod, where the direction is reversed and theventilation air then flows, together with the smoke from the tobacco rod12, through the filter plug 16 into the smoker's mouth.

If the plug wrap is air-permeable, either inherently porous or providedwith ventilation openings, then an adjustable portion of ventilation airflows by this flow path through the air-permeable plug wrap into thefilter and to the mouth of the smoker. This is in addition to the airflowing through the grooves 20. In this way the dilution of the smokecan be adjusted by air ventilation in two places, i.e. firstly byventilation through the tipping paper 22 and along the grooves 20, andsecondly by ventilation air which enters directly through the plug wrap18 into the filter plug 16.

If necessary, further short grooves open only to the mouth side of thefilter 14 can be impressed into the exterior surface of the tippingpaper 22. These have no rheological function, since they are notconnected with the ventilation zone 24, but only alert the smoker to thepresence of grooves in the filter element 14.

FIG. 2 shows a graph of the effect of the filter ventilation on theCO/tar ratio with a filter in accordance with the invention fromconventional cellulose acetate filter tow, an air-impermeable plug wrapand four grooves 20 with the above dimensions, which are symmetricallydistributed over the circumference of the filter plug 16 and which,commencing from the tobacco end, extend over 60% of the length of thefilter element 14.

In experiments the ventilation of the filter element 14 was varied,namely from zero to a maximum ventilation degree of 70%. For products of3 mg or less it is necessary, in order to obtain the requiredventilation level, to use additional on machine laser perforation, aswell as pre-perforated tipping. This increased ventilation level alsohelps reduce cigarette pressure drop. The reduction in CO/tar ratioobtained is balanced with the level of ventilation used.

In FIG. 2 the full circles indicate the measured values for aconventional filter made from monoacetate filter tow without grooves,while the squares describe the measured values for a filter element 14in accordance with the invention with the structure and the samedimensions as the comparison filter described above.

One can recognize very well that the filter element 14 in accordancewith the invention reduces the CO content of the smoke relative to thedelivered tar and hence the CO/tar ratio from about 1.4 to about 0.7,while through ventilation alone, and hence without use of grooves, theCO/tar ratio can be lowered to only to about 1.12.

Thus the CO/tar ratio can be reduced to below the limit set by the newregulations with the filter element 14 in accordance with the inventionby the appropriate selection of a suitable degree of ventilation for thetipping paper 22.

Additional investigations of cigarettes with filters according to thisinvention showed that these results were confirmed also for differenttobacco blends in the tobacco section of the cigarette. In Tables 1-3the results are shown for the tobacco column of three commerciallyavailable cigarettes to which the filter of this invention was added.The corresponding cigarettes with conventional filters gave tar levelsof about 10 mg, 6 mg, and 3 mg respectively. The measurements were donefollowing DIN and ISO standards.

The filters used for these measurements had the following parameters ofthe grooves: 4 grooves, 17 mm long, about 1.5 mm wide and 0.5-1 mm deep.The plug wrap was air impermeable and not additionally ventilated.

The findings show clearly that the filters of this invention (named EF)made it possible to produce cigarettes with comparable pressure drops tothe cigarettes with standard filters (named SF) by adjusting theventilation level, but with clearly reduced CO/tar ratios.

TABLE 1 SF EF EF EF EF EF Pressure drop 72 76 76 74 73 72 filter inmm(H₂0) Filter ventilation 22.6 0.0 12.0 51.8 57.2 62.1 tar in mg 10.2512.4 11.7 8.8 7.2 5.7 CO in mg 11.21 13.3 12.1 6.7 4.5 2.9 Pressure drop117 137 121 104 93 93 cigarette in mm(H₂0) CO/tar 1.09 1.07 1.03 0.760.63 0.51

TABLE 2 SF EF EF EF EF Pressure drop 108 90 89 91 89 filter in mm(H₂0)Filter ventilation 43.0 0.0 50.6 58.3 69.1 tar in mg 5.6 11.4 7.8 6.14.3 CO in mg 6.7 13.1 5.8 3.5 1.8 Pressure drop 112 144 114 110 107cigarette in mm(H₂0) CO/tar 1.19 1.15 0.74 0.57 0.42

TABLE 3 SF EF EF EF EF Pressure drop 124 100 98 99 98 filter in mm(H₂0)Filter ventilation 56.7 0.0 45.2 51.1 62.5 tar in mg 3.33 8.8 6.3 5.24.4 CO in mg 4.24 11.3 5.4 3.6 2.6 Pressure drop 107 144 125 121 120cigarette in mm(H₂0) CO/tar 1.27 1.28 0.86 0.69 0.59

FIG. 3 shows in cross section a filter element 14 of the invention,where like parts are labelled in accordance with FIG. 1, attached to atobacco rod 12. The plug wrap 18 used to overlie the filter plug 16includes a portion that has particulate activated carbon adhered theretoin the region 26. Grooves 20 are formed in the plug wrap 18 after theplug wrap is wrapped around the filter plug 16. The filter element isthus an integral element.

An alternative embodiment along the same theme is shown in FIG. 4.However, in this embodiment the filter element comprises three sections:a grooved section in which grooves 20 are formed in the surface thereof,a Dalmatian carbon section 28 comprising particles of activated carbondispersed in cellulose acetate tow, and a conventional cellulose acetatetow section 30. The three sections may be joined together by one plugwrap which is mouldable to produce the grooves of the grooved section.Alternatively, the grooves are formed in the surface of either aself-sustaining non-wrapped acetate (NWA) section or a plug wrapenwrapping a cellulose acetate section. The three sections are thenaligned together and then overwrapped with a further plug wrap (notshown).

The embodiments of FIGS. 3 and 4 avoid the problem of having to mouldgrooves into a filter section containing particulate matter, duringwhich moulding there may be adverse effects on the particulate matter ifcontacted with heating elements. However, it is possible to thermallyform grooves in a carbon-containing section, particularly if use is madeof a thermoformable plugwrap, and such is an option open to thecigarette designer.

In addition, the presence of additive material affects other vapourphase, constitutents and can be particularly advantageous for theselective removal of some of those compounds on the Hoffmann analytelist (see Hoffmann, D., Hoffmann, I., “Tobacco Smoke Components”,Beitrage ziir Tabakforschung International 18 (1998) 49).

1. A smoking article incorporating a filter (14) for the reduction ofthe CO/tar, ratio delivered during smoking comprising a cylindricalfilter plug (16) of filtration material; a plug wrap of air-impermeablematerial (18) around the filter plug (16); the filter comprising a firstsection having circumferentially spaced grooves (20) extendinglongitudinally along the first section of the filter plug (16) and alsoimpressed into the plug wrap (18); and a ventilated tipping paper,connecting the filter plug (16) to a tobacco rod (12); and all of saidgrooves (20) being open to the tobacco rod (12) of said smoking articleand extending continuously only over about 60% of the length of thefilter plug (16) and separated from the mouth end of the filter (16);and wherein all grooves (20) are covered with the ventilated tippingpaper (22) such that ventilating air entering said grooves (20) throughsaid ventilated tipping paper (22) flows toward the tobacco rod and intosaid filter plug during smoking, wherein the grooves (20) do not connectwith each other, the filter further comprising a second section alignedwith the first and receiving air from the first section during smoking,wherein the second section comprises particles of activated carbon, andthe first section does not contain particles of activated carbon.
 2. Asmoking article in accordance with claim 1, wherein the filtrationmaterial of filter plug (16) is homogeneous over the full length of thefirst section of the filter plug (16).
 3. A smoking article inaccordance with claim 1, wherein two to ten grooves (20) are provided.4. A smoking article in accordance with claim 3, wherein three to fivegrooves are provided.
 5. A smoking article in accordance with claim 4,wherein four grooves are provided.
 6. A smoking article in accordancewith claim 1, wherein the grooves (20) are distributed symmetricallyover the circumference of the filter plug (16).
 7. A smoking article inaccordance with claim 1 wherein the grooves (20) are V-shaped orU-shaped.
 8. A smoking article in accordance with claim 1, wherein thegrooves have a depth from 0.5 to 2 mm.
 9. A smoking article inaccordance with claim 1, wherein the grooves (20) at the circumferencehave a width of 1 to 3 mm.
 10. A smoking article in accordance withclaim 9, wherein the grooves (20) at the circumference have a width offrom 1.5 to 2.5 mm.
 11. A smoking article in accordance with claim 1,wherein the filter plug (16) comprises filter tow made of celluloseacetate.
 12. A smoking article in accordance with claim 1, wherein thefilter plug (16) contains additives selected from the group consistingof activated charcoal, zeolites, Duolite, flavor modifiers orcombinations thereof.
 13. A smoking article in accordance with claim 1,wherein the tipping paper (22) is porous.
 14. A smoking article inaccordance with claim 1, wherein the tipping paper (22) is provided withventilation openings (24) by mechanical or electrostatic means or bylaser beams.
 15. A smoking article in accordance with claim 1, whereinthe plug wrap of air-impermeable material is provided with ventilationopenings.
 16. A smoking article in accordance with claim 15, wherein theventilation openings are provided by on-line machine perforation.
 17. Asmoking article in accordance with claim 1, wherein the degree ofventilation provided to the smoking article by the tipping paper liesbetween 30% and 80%.
 18. A smoking article in accordance with claim 1wherein the degree of ventilation provided to the smoking article by thetipping paper lies between 40% and 70%.